Prime minister Boris Johnson is expected to announce most Covid protection measures, including social distancing rules, will remain in place for another four weeks after the planned 21 June unlock.
Senior ministers have reportedly signed off on the decision to delay the lifting of all legal restrictions on social contact, the BBC reports.
It could mean a further day to the resumption of international travel. The extension will be put to a House of Commons vote later this month.
It comes amid increasing concern over the emergence of the Delta variant of Covid-19, which according to the BBC now accounts for 90% of all new Covid infections in the UK.